1. Technical Field
The present invention relates generally to an organic light emitting device.
2. Related Art
Recently, as demands for lighter or thinner monitors or TVs have been increasing, cathode ray tubes (CRTs) are being replaced by flat panel displays (FPDs). Typical flat panel displays include a liquid crystal display, a field emission display, an organic light emitting device, and a plasma display panel.
Among the flat panel displays, the organic light emitting device has been receiving attention because of its low power consumption, fast response speed, wide viewing angle, and high contrast ratio. The organic light emitting device as a self-emissive display device includes two electrodes and an organic light emitting layer interposed between the two electrodes. One of the two electrodes injects holes and the other injects electrons into the light emitting layer. The injected electrons and holes are combined to form excitons, and the excitons emit light as discharge energy.
Generally, the luminance of the organic light emitting device is proportional to the area of the organic emission layer such that it is necessary to obtain a high aperture ratio to increase the luminance of the organic light emitting device. On the other hand, a storage capacitor to maintain a data signal of the organic light emitting device is necessary. If a gate-on voltage is applied to a switching transistor of the organic light emitting device, the data signal from the data line is input to a control terminal of the driving transistor. The organic light emitting member flows a current having a magnitude depending on a difference between the data signal and a driving voltage. The storage capacitor charges the data signal input to the control terminal of the driving transistor and maintains it after the switching transistor is turned off. To stably supply the current, it is important to maintain the data signal. Accordingly, it is preferable that the storage capacitance of the storage capacitor of the organic light emitting device is large.
Generally, the organic light emitting device includes a storage electrode and a storage electrode line to form the storage capacitor. The capacitor includes two conductive layers overlapping each other via an insulating layer therebetween, and the storage capacitance is proportional to the area of the two conductive layers such that the storage electrode and the storage electrode line have a wide area to form the storage capacitor having the high storage capacitance. However, the storage electrode and storage electrode line are simultaneously formed with the same layer as the opaque signal line such that the aperture ratio of the organic light emitting device is reduced according to the increase of the area of the storage electrode and the storage electrode line.
The above information disclosed in this background section is for enhancement of understanding of the background of the invention, and therefore, it may include information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.